<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      .box {
        width: 200px;
        height: 200px;
        background-color: #f20;
        margin: 0 auto;
        box-shadow: inset 0px 0px 0 10px #0f0, 0px 0px 0 20px #00f;
        /* box-shadow:(inset) 水平偏移量 垂直偏移量 模糊半径 扩张半径 阴影颜色*/
      }
    </style>
  </head>
  <body>
    <div class="box"></div>
  </body>
</html>

